diff --git a/bin/unzip b/bin/unzip
new file mode 100755
index 0000000..581ff8e
Binary files /dev/null and b/bin/unzip differ
diff --git a/models/problem.js b/models/problem.js
index 1e6a32f..bafd72b 100644
--- a/models/problem.js
+++ b/models/problem.js
@@ -340,7 +340,8 @@ class Problem extends Model {
       await fs.remove(dir);
       await fs.ensureDir(dir);
 
-      await p7zip.extract(path, dir);
+      let execFileAsync = Promise.promisify(require('child_process').execFile);
+      await execFileAsync(__dirname + '/../bin/unzip', ['-j', '-o', '-d', dir, path]);
       await fs.move(path, this.getTestdataArchivePath(), { overwrite: true });
     });
   }